Carboxyalkylbenzene sulfonic acids and carboxynitroalkylbenzene sulfonic acids and alkali metal salts thereof



United States Patent Ofifice 2,698,864 Patented Jan. 4, 1955 CARBOXYALKYLBENZENE SULFONIC ACIDS AND CARBOXYNITROALKYLBENZENE SUL- FONIC ACIDS AND ALKALI METAL SALTS THEREOF Carl B. Linn, Riverside, and George L. Hervert, Downers Grove, Ill., assignors to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware No Drawing. Application November 21, 1950, Serial No. 196,938

12 Claims. (Cl. 260-507) This invention relates to surface active agents and methods for producing the same. More particularly this invention relates to a composition of matter formed by treating a long-chain alkyltoluene sulfonic acid with .dilute nitric acid at an elevated temperature and to esters and salts of said composition of matter.

An object of this invention is to oxidize a long-chain alkyltoluene sulfonic acid with an aqueous solution of nitric acid.

Another object of this invention is to form a surface active agent comprising carboxyalkylbenzene sulfonic acid, carboxynitroalkylbenzene sulfonic acid and alkali metal salts of said sulfonic-acids.

A further object of this invention is a carboxydodecylbenzene sulfonic acid.

A still further object of this invention is a carboxynitrododecylbenzene sulfonic acid.

One embodiment of this invention relates to a process for producing a surface active agent which comprises reacting a long-chain alkyltoluene sulfonic acid with an aqueous solution of nitric acid at a temperature sufficient to effect oxidation as the principal reaction of the process.

Another embodiment of this invention relates to a process for producing a surface active agent which comprises reacting an alkyltoluene sulfonic acid in which the alkyl ing aqueous solution of nitric acid, neutralizing the resultant product with a base to form a salt, and recovering said salt having surface active properties.

A still additional embodiment of this invention relates 'to a process which comprises reacting an alkyltoluene sulfonic acid in which the alkyl group contains from about 6 to about 18 carbon atoms with an aqueous solution of nitric acid at a temperature sufficient to oxidize the methyl group to a carboxylic acid group and to form a product containing at least one member of the group consisting of a carboxyalkylbenzene sulfonic acid and a carboxynitroalkylbenzene sulfonic acid, converting said product into a surface active material comprising at least one member of the group consisting of a polyalkylene glycol ester and an alkali metal salt of a carboxyalkylbenzene sulfonic acid and a carboxynitroalkylbenzene sulfonic acid, and recovering said surface active material.

We have found that a long-chain alkyltoluene sulfonic acid in which the alkyl group contains from about '6 to about 18 carbon atoms may be converted into an improved surface active agent by an oxidation treatment with a dilute aqueous solution of nitric acid at an elevated temperature. This treatment is carried out at a temperature of from about to about 150 C., and preferably at a temperature of from about 80 to about 120 C. and at a pressure sufficient to keep the reactants and nitric acid solution in substantially liquid phase. The operating temperature, the time of treatment, and the concentration of nitric acid are so controlled that the main reaction is oxidation rather than nitration. The aqueous nitric acid solution used in this process contains from about 1 to about 25% by weight of HNO3 and preferably from about 5 to about 15% by weight of HNO3.

This process is useful in converting long-chain alkyltoluene sulfonic acids into improved wetting agents and detergents by controlled oxidation treatment utilizing an aqueous solution of nitric acid as the oxidizing agent. The oxidation products so formed contain carboxyalkylbenzene sulfonic acids and carboxynitroalkylbenzene sulfonic acids which have improved surface active properties or may be converted into alkali metal salts particularly the sodium salts. Also the aforementioned sulfonic acids and their salts may also be utilized as intermediates in the production of other organic compounds. Thus the carboxyalkylbenzene sulfonic acids and carboxynitroalkylbenzene sulfonic acids may be esteritied with alkanols, glycols and other polyhydric alcohols. Such esters formed by reacting the above-mentioned sulfonic acids with polyalkylene glycols as polyethylene glycol have good surface active, wetting, penetrating and detergent properties. These esters formed by reacting a polyalkylene glycol with a carboxyalkylbenzene sulfonic acid and a carboxynitroalkylbenzene sulfonic acid are non-ionic surface-active agents and in some of these compounds the presence of one or more nuclearly substituted nitro groups produce a surface-active material with a desirable balance between its hydrophilic and lipophilic properties. However other polyalkylene glycol esters may also lie utilized similarly including those of polypropylene g yco These esters may be formed by the esterification of the corresponding carboxyalkylbenzene sulfonic acid or carboxynitroalkylbenzene sulfonic acid with a polyalkylene glycol or by the direct condensation of the acid with the desired amount of an alkylene oxide in the absence of a catalyst or in the presence of a slightly basic catalyst such as sodium acetate.

The oxidation treatment of this process may be carried out in either batch or continuous types of operation. In a typical batch-type operation, the alkyltoluene sulfonic acid and aqueous solution of nitric acid are mixed in a suitable reactor provided with a mechanically driven stirrer or other suitable mixing equipment and the resultant mixture is maintained at a temperature of from about 50 to about 150 C. for a time suflicient to oxidize the methyl group of the alkyltoluene sulfonic acid to a carboxyl group. During this treatment the benzene nucleus of the alkyltoluene sulfonic acid may undergo a certain amount of nitration as well as oxidation of the methyl group thus producing a carboxynitroalkylbenzene sulfonic acid admixed with a carboxyalkylbenzene sulfonic acid. The resultant oxidation product may contain from about 5 to about by weight of the carboxyalkylbenzene sulfonic acid and from about 95 to about 5% by weight of the carboxynitroalkylbenzene sulfonic acid depending upon the conditions of operating temperature, nitric acid concentration, and duration of the oxidation treatment. These different mixtures of carboxyalkyland carboxynitroalkylbenzene sulfonic acids and particularly mixtures of carboxydodecyland carboxynitrododecylbenzene sulfonic acids have high surface active properties and are useful as detergents particularly for removing soil from soiled cotton cloth and the like.

The oxidation treatment of a long-chain alkyltoluene sulfonic acid may also be carried out by passing this sulfonic acid and an aqueous solution of nitric acid through a suitable tubular reactor provided with adequate mixing means and maintained at an oxidation temperature of from about 50 to about C. The time employed in this oxidation treatment is controlled by the volume of the reactor and by the rates at which the charged alkyltoluene sulfonic acid and aqueous nitric acid solution are passed therethrough. These factors are so controlled that oxidation of the methyl group can be made the principal reaction of the process with a minor amount of nitration of the benzene ring of the compound being treated. The mixture of reaction products is discharged from the tubular reactor and is then subjected to suitable separation means in order to recover the carboxyalkylbenzene sulfonic acid and carboxynitroalkylbenzene sulfonic acid or these sulfonic acids are treated with an aqueous solution of an alkali metal compound to form alkali metal salts of the carboxyalkylbenzene sulfonic acid and carboxynitroalkylbenzene sulfonic acid formed in the oxidation.

The nature of this invention and type of results obtained are illustrated further in the following example which should not be misconstrued to limit unduly the general broad scope of the invention.

. A 1 liter flask provided with a reflux condenser was charged with 300 cc. of water, 50 cc. of nitric acid containing 70% by weight of HNOs, and 26 grams of a dodecyltoluene sulfonic acid produced by sulfonation of an alkylate formed by reacting toluene with propylene tetramers in the presence of sulfuric acid at a temperature After the mixture of dodecyltoluene sulfonic acid and aqueous nitric acid was heated to the boiling point, the solution first became homogeneous, then later appeared milky or turbid and nitric oxide fumes appeared. The refluxing was continued for several hours during which a white solid appeared in the flask. The refluxing was continued for a total time of 136 hours without further evidence of a change in the reaction mixture. resultant reaction product was then placed in an evaporat- The ing dish on a steam bath and evaporated to a volume of about 75 cc. Then 400 cc. of water was added to the contents of the evaporating dish and evaporation was continued until the volume was reduced again to about This dilution-evaporation procedure was repeated 75 cc. 3 times. The syrupy residue which remained in the evaporating dish was extracted twice with ether, thus removing 3 grams of ether soluble material. The aqueous solution of the rattinate was dehydrated by placing it under reduced pressure (1 mm.) and slowly Warming to 70 C. The product which remained weighed 20 grams. This was a hygroscopic light brownish yellow syrup which formed an aqueous solution that foamed readily and formed an insoluble calcium salt.

Titration data obtained on this syrupy product showed it to have an equivalent weight of 214 which corresponds closely to a calculated equivalent weight of 204 corresponding to the formula NO: SOaH The carboxynitroalkylbenzene sulfonic acid may thus contain a nitro group and a sulfonic acid group bound to the benzene ring as indicated in the above formula. How- I ever other experimental results on this reaction product also indicate that these carboxynitroalkylbenzene sulfonic acids may also have a nitro group combined with a carbon atom of the long alkyl side chain, that is, with a highly substituted carbon atom of the dodecyl group. The potentiometric titration curve of the syrupy product referred to above was in accord with the above-indicated structures of a carboxynitroalkylbenzene sulfonic acid in that both a strong acid (sulfonic) and a weak acid (carboxy) are indicated. Elementaryanalysis of the oxidation prodnot represented by the above formula are as follows:

Found: percent S, 8.30; percent N, 1.73

Both the free acid and the sodium salt of the aboveindicated mixture of carboxydodecylbenzene sulfonic acid (A) and carboxynitrododecylbenzene sulfonic acid (B and :1 C) have good detergent properties but the salt mixture is somewhat more effective than the mixture of the sulfonic acids. This detergent activity is also higher than that of the dodecyltoluene sulfonic acid charged to the process.

We claim as our invention:

1. A surface-active material comprising a mixture of carboxyalkylbenzene sulfonic acid and carboxynitroalkylbenzene sulfonic acid in Which'the alkyl group and the carboxy group are each attached to the benzene ring and the alkylgroup contains from about 6 to about 18 carbon atoms.

2. A surface'active material comprising a mixture of the sodium salts of carboxydodecylbenzene sulfonic acid and carboxynitrododecylbenzene sulfonic acid in which the carboxy group and the dodecyl group are each attached to the benzene ring.

3. A surface-active material comprising at least one compound selected from the group consisting of carboxyalkylbenzene sulfonic acid in which the carboxy group is attached to the benzene ring, carboxynitroalkylbenzene sulfonic acid in which the carboxy group is attached to the benzene ring, and the alkali metal salts of said acids, the alkyl group of said compound being attached to the benzene ring and containing from about 6 to about 18 carbon atoms.

4. A surfaceactive material as defined in claim 1 further characterized in that said alkyl group is dodecyl.

5. A surface-active materialcomprising carboxyalkylbenzene sulfonic acid in which the alkyl group and the carboxy group are each attached to the benzene ring and the alkyl group contains from-about 6 to about 18 carbon atoms.

6. A surface-active material comprising an alkali metal salt of carboxyalkylbenzene sulfonic acid in which the alkyl group and the carboxy group are each attached to the benzene ring and the alkyl group contains from about 6 to about 18 carbon atoms.

7. A surface-active material comprising carboxydodecylbenzene sulfonic acid in which the carboxy group and the dodecyl group are each attached to the benzene ring.

8. A surface-active material comprising an alkali metal salt of carboxydodecylbenzene sulfonic acid in which the carboxy group and the dodecyl group are each attached to the benzene ring.

9. A surface-active material comprising carboxynitroalkylbenzene sulfonic acid in which the alkyl group and the carboxy group are each attached to the benzene ring and the alkyl group contains from about 6 to about 18 carbon atoms.

30. A surface-active material comprising an alkali metal salt of carboxynit-roalkylbenzene sulfonic acid in which the alkyl group and the carboxy groups are each attached to the benzene ring and .the alkyl group contains from about 6 to about 18 carbon atoms.

11. A surface-active material comprising carboxynitrododecylbenzene sulfonic acid in which the carboxy group and the dodecyl group are each attached to the benzene ring. a

12. A surface-active material comprising an alkali metal salt of carboxynitrododecylbenzene sulfonic acid in which the carboxy group and the dodecyl group are each attached to the benzene ring.

References'Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Bauer: Annalen, vol. 220, pp. 18-25 (1883). Beilstein, vol. 11, page 401. 

1. A SURFACE-ACTIVE MATERIAL COMPRISING A MIXTURE OF CARBOXYALKYLBENZENE SULFONIC ACID AND CARBOXYNITROALKYLBENZENE SULFONIC ACID IN WHICH THE ALKYL GROUP AND THE CARBOXY GROUP ARE EACH ATTACHED TO THE BENZENE RING AND THE ALKYL GROUP CONTAINS FROM ABOUT 6 TO ABOUT 18 CARBON ATOMS. 